This invention relates to railroad cars and particularly to articulated railroad cars and to side bearing units used therewith. A side bearing unit is attached to the bolster of each truck whereby regulating independent movement of the body of the car and impeding truck hunting. Side bearing units have been used to regulate movement between the body of a railroad car and the trucks for a substantial period of time. These side bearing units are of various designs and structure as based upon the type of car they are associated with, the weight it carries, etc.
Recently, a new type of railroad car has been put into service which creates unique demands upon the side bearing employed. These cars are generically known as articulated cars, they are lightweight, of high technology design and offer a new series of challenges for side bearings For example, it has been found that the connectors between the articulated cars are prone to wear, whereby the male end of the articulated connector will tend to settle and, in fact, lose as much as 3/8" in vertical height. This results in lowering of the male end of the car body relative to the side bearing. The drop in vertical height has the potential of compressing a standard side bearing beyond its normal limits of travel and thus render it useless for its designed objective. For example, the weight of the entire car will be carried by the side bearings and not by the center plate of the bolster. A further demand use for increased travel on articulated cars has been found when the car is run through a super elevated curve. Articulated cars with standard 5/16" travel constant contact side bearings have been noted to derail while passing through such a curve.
In articulated car applications, there is a necessity of mounting the side bearings off the centerline of the bolster. This may result in a twisting moment in the bolster, thus requiring increased side bearing travel Increased side bearing travel is one of the situations which must be satisfied in articulated car service. The side bearing of this invention addresses this problem in a way in which no other side bearing has been designed to accomplish. It should be noted that side bearings used today in interchange must meet all of the requirements of the Association of American Railroads M-948 Specification.